The advisability of calibrating only carefully selected thermometers is emphasized. The relation between calibration point spacing and the weighting method used in curve fitting the calibration is discussed and then illustrated by various fits to different data sets for a particular germaniumthermometer. Apart from different end effects, which could be minimized by a higher density of points at each end of the range, there is little significant difference between the results of the various methods tried.

An improved analysis of continuous wave (cw) NMR detection by Q‐meters is presented which explicitly includes parallel resistive loading of the sample coil and frequency dependent losses caused by the rf skin effect. A versatile MOSFET Q‐meter is described which operates at frequencies up to 60 MHz and rf input levels between 2 and 100 mV peak‐to‐peak. The noise figure is shown to be less than 3 dB at 8 MHz and a 7 mV peak‐to‐peak rf level. A comparison of Q‐meters with other types of cw NMR detectors is given, and their advantages for accurate line‐shape and susceptibility experiments are discussed.

A new quartz laser tube, which can operate at 1000°C for metal vapors, has been built. The tube was operated in a three‐zone oven, with the Brewster windows at a slightly higher temperature than the main laser body. Thus, a buffer gas was not necessary to prevent condensation of the metal on the windows. A technique for fusing the quartz windows to the quartz tube, without degrading the optical flatness, has been developed. Molybdenum ribbons fused into quartz cylinders provide vacuum‐tight electrode connections.

A high pressure microcalorimeter based on the differential scanning calorimeter(DSC) principle is described. In the present investigation this device was used for the determination of heats of transformation at pressures up to 2200 bar. The procedure for calibrating this apparatus is discussed. The temperature accuracy is considered to be ± 1 K in the range from −20 ° to +200 °C and to be about ± 5% for the determination of heats of transformation.

An alumina‐filled casting epoxy (trade name Stycast) was found to reliably seal to thin stainless steel edges and 1 mm diam stainless steel feedthrough pins. All seals retained their integrity after typically 50 cycles from −196 ° to 20 °C and 10 cycles from −196 ° to +100 °C. Several chambers were constructed using the epoxy both as a vacuum‐tight wall and as an electrical insulator for a large number of multi‐kV feedthroughs. The largest of these was 18 cm in diameter and contained 125 feedthrough pins. The chambers were immersed in a Freon‐11 bath at −105 °C, filled with liquid xenon, and tested for the presence of electronegative impurities. After degassing, the contamination levels measured were slightly higher than those we commonly observe for chambers constructed only of glass and metal.

A passive dosimetric technique was used which maps electron current density with a spatial resolution of 0.013 cm at 300 keV. Electron divergence and emittance angles are distinguished and can be mapped at any point in an intense electron beam with an accuracy of 10%. The technique applies to beams of up to 50 kA/cm2 and 100 keV–3 MeV.

A spectrometer for making absolute absorptionmeasurements is described. The system is especially suitable for work with solid state samples at low temperatures. Both sample and reference beams pass through the same set of Dewar windows, making compensation for the losses in these unnecessary. Simplicity and low cost are achieved by using a chopper wheel of special configuration rather than the usual rotating mirror. Direct measurement of optical densities as high as 4.0 is possible.

The fabrication of highly characterized DT‐filled, hollow glass microsphere targets is described. The DT is loaded by gas permeation through the glass walls at 420 °C. The DT fill is nondestructively measured by counting the emitted x rays with a proportional counter. The counter system is empirically calibrated by individually crushing microspheres in an ionization chamber. Outer diameters are measured optically with a split‐image eyepiece. Wall thicknesses and sphericities are measured by light interference. For a 40‐μ diam microsphere and 1‐μ walls, we estimate our best absolute accuracies of measurement to be, o.d., ±1.6%; wall thickness at any point, ±10%; overall microsphere sphericity, ±7%.

With the advent of high speed computers, the digital processing of data became a common practice among many researchers. The recent trend among geophysicalresearchers has been to establish their own computer system by use of a minicomputer rather than time sharing of a larger system. In developing such a system, a question arises as to how reliable is the newly acquired computer system. A method of evaluating the performance of such a computer system is presented. The method consists of processing data of known characteristics and comparing the results. The quantities calculated include probability densities, higher order moments, spectra, cross spectra, and a coherency spectrum.

The observation of the light emission due to the chemiluminescent gas phase oxidation of phosphorus gives information on the stirring of gaseous fluids in real flow reactors. Three types of reaction vessels have been tested.

A simple electro‐optical angular displacement transducer for use in a torsion pendulum is described. It uses the changing light intensity transmitted through two polarizers, which are rotating against each other as the sample undergoes damped sinusoidal oscillations, to produce a voltage output linear in angular displacement over a range of 10 °.

Secondary electron ejection coefficients for rare gas metastable atoms striking a stainless steel surface have been determined using an improved gas cell technique. Data are presented for He(2 1S), He(2 3S), and Ne(3P0,2) atoms, and limitations of this technique are discussed. An alternative method for γ determination is described which utilizes laser induced photoionization rather than chemiionization, and results are presented for He(2 1S) and Xe(3P0).

Design, construction, and performance of a balloon borne low temperature air sampler are described. The sampler can collect 16 samples of 10 liter STP at different stratospheric altitudes. The collected samples allow measurement of the trace gases H2, H2O, CH4, CO, CO2, and N2O. In the future, measurements will include the Freons, CCl4, SF6, CH3OH, and ΣNOx; also, the altitudes will be extended from the present 35 km to above 45 km.

We present the design and development of a differential laser spectrometer capable of the accurate measurement of very small changes in the translational diffusion coefficients (DT) of macromolecules. Since DT depends solely on the translational frictional coefficient of a macromolecule, this parameter is a direct measure of macromolecular conformation, and thus detection of small changes in the translational diffusion coefficient can reveal very slight conformational alterations. The differential laser probe we present is a differential optical mixing laser spectrometer capable of the direct measurement of the difference in the spectra of the light scattered by two solutions of macromolecules and hence, the difference in the translational diffusion coefficients of the macromolecular species under investigation. In its present form, the instrument has a precision of 3 parts in 103, that is, the differential laser probe can measure a change in DT of 3% with a precision of 10%. Discussion is provided for the system improvements required to increase the precision one additional order of magnitude.

The modulation of the dynamic polarization is used to measure the longitudinal nuclear relaxation. This method is complementary to the rf pulse technique and combines the advantages of the dynamic nuclear polarization (DNP) enhancement and the high signal/noise from narrow band detection. The DNP spectrometer with microwave modulation is described and the results of its application to a fluorine–electron system are compared with those from the conventional pulse technique.

The design of a Stark resonant cell and the microwave spectrometer used with it are described. The features of the cell are its simplicity, ease of construction, and convenient size. The method of maintaining the cell on tune is discussed. Performance is expressed in terms of results obtained for two lines in the spectrum of D2O.

A K‐band time domain microwave spectrometer with a plane parallel Fabry–Perot resonator external to the gas cell is described. A time domain emission technique consisting of a two pulse sequence of a long saturating pulse followed by a short π/2 pulse is used to measure energy relaxation times, which are the Fourier transform of pressure and wall collision broadened linewidth independent of Doppler broadening. The flexible resonator configuration yields sensitivities comparable to waveguide spectrometers with various gas cells suitable for collision studies or ir‐double‐resonance experiments.

The system described functions as a sensitive gas volume meter while automatically keeping the pressure at a constant level. It is based on the simplest hydraulic principles and may be adjusted to work at different pressure levels. Accuracy is better than 0.5% at atmospheric pressure. As the system is cheap to construct, significant experimental time may be saved by incorporating several units in parallel. Reference is also made to possible fields of application.

A high pressure air gap is used as a fast ’’crowbar’’ switch with the aid of a low pressure gap decoupler. In order to trigger the switch, a special trigger circuit is designed, in which a single pulse breaks down the high and low pressure gaps successively. The jitter of breakdown time of this switch is less than 20 nsec over a wide range of operating conditions, pressures in both gaps, and working voltage. The switch is designed for 40 kV operation. Its inductance is 22 nH, and the resistance at a current of 40 kA is 4 mΩ. Seventy switches are installed in a 40 kV, 210 kJ fast bank. Up to now they have been running for about 20 000 shots with little maintenance.